Method of tanning



United States Patent-O p .1 2,923,594 Murnoo F. TANNiNG' Emanuel R. Liebrinan, 's'anieiviile, and an v. Fagan,

New Brunswick, N J assignors to Ethicon, Inc., a corporation of New Jersey Ne Drawing. I Application May 29, 1958 Serial N6. 738,598

14 Claims. (c1. s 94.11

surgical procedures because it is absorbed tooi' Patented Feb. 2, 1960 0.25%,and about 5%, preferably about 1%, and the catgut, in a ratio from about 1:1 to about 1:100, preferably about 1:1,0, based on the ratio of dry weight of gut to volume of tanning solution (advantageously in the form of ribbons of suitable length) is submerged in the solu-' tion. The gut is kept immersed in the solution for a periodfrom about fifteen minutes to about twelve hours or more, preferably about three hours. moved, washed,and converted into string byconventional methods The surprising feature of our novel process rests on the: fact that the isocyanate reacts with the catgut even though it is present in an aqueous system. Under these conditions one would, normally expect that the isocyanate would react with the aqueous phase, which is in a large: excess as compared with the amount of catgut; The

application'of heat is not only unnecessary, but also in rapidly and the suture is disintegrated before the wound has had an opportunity to heal properly. For this reason, atype of catgut is manufactured which is treated with socalled tanning agents, the purpose of which is to combine irreversibly with the gut andform a chemically rearranged protein material which is more resistant to enzymatic attack, retains its initial strength for a longer jurious to the'g'utl v It'isto be noted that the noveltyof theprocess resides: in the use oftolylene diisocyanate; n-butyl-isocyanate and hexamethylene diisocy'anate in the for'm of their bisulfite:

; addu'ctjs. None of these isocyanates can be conveniently employed as such as tanning'agents; since they are lachrimatory, water-insoluble and extremely diflicult to handle. It is to beunderstood, furthermore, that the term tolylene diisocyanate' as fused in this invention is intended to mean any one or a mixture of the available isomers of period of time after being inserted into the body, and

thus holds the wound together for a longer time during the wound healing period. 9

- Many theories have been postulated regarding the mechanism-of tanning, depending on the tanningage'nt employed. Vegetable tanning with tannin, for example is believed to be predicated on the ability of the large tannin'molecule to fix itself by hydrogen-bondingbement of coordinately combined anionic groups. One disadvantage of chrome tanning resides in the danger at tached to the use of heavy metal, which is known to 'be toxic.

tolylene diisocyanate, i.e.the 2,4 isomer, the 2,6 isomer, etc. It will be observed also that although the examples below illustrate the-preparation of sodium bisulfiite ad. ducts, other alkali metal bisulfite adducts,e.g. potassium bisulfite adduct, may be preparedin alike manner.

of the catgut suture.

PREPARATION OF TOLYLENE DIISOCYANATE- SODIUM BISULFITE ADDUCT To a solution. of 40 grams of sodium bisulfite in 60 ml. of water contained in a 250 ml. flask fitted with a- One of the commonly used tanning agents is formaldehyde. This relatively simple and easily obtainable chemical, which apparently forms a reaction product with the free amino groups of the collagenous catgut, is an extreme- 1y obnoxious reagent which is;difilcult to handle, highly irritating, and toxic. Moreover, there have been reports to the elfect that it is erratic in its tanning effects. on gut and, for this. reason, requires carefully controlled conditions to produce desirable results. ,Finally, it is,

well known that formaldehyde-tanned catgut leaves much handle, non-irritating, water soluble ,crystallinesolids) Moreover, and perhaps more importantly, in processes employing these compounds one can obtain a tanned catgut product which has a superior dry knot tensile strength while retaining an in vivo absorption time comparable tothat of presently available tanncd gut. 1' I In accordance With".0l'l embodiment of the novel process, the bisulfite adduct of tolylene. diisocyanate,*n-=

butyl-is'oc yanate or hexamethylene diisocyanate is dissolved in water -in an amount varying between :about stirrer and thermometer are added 27 grams of tolylene diisocyanatefl The temperature is maintained at or below 25 C. during the,reaction. After one-half hour, the mixture thickens and heat is evolved. Stirring is continued for an additional one and one-half hours, after which time. 60ml. of water are added. When all the solid has dissolved, the solution is filtered. Methyl alcohol is added tothe filtrate until the precipitation of tolylene diisocyanate-sodium bisulfite is complete. h The solid is filtered, washed thoroughly with methanol, and dried in a vacuum desiccator over phosphorus pentoxide to remove any traces of moisture still present. Yield 57 grams.

In the same manner, using hexamethylene diisocyanateas the starting material, the hexamethylene diisocyanatcsodium bisulfite adduct is prepared.

PREPARATION OF n-BUTYLISOCYANATE} SODIUM BISULFITE ADDUCT To a solution of 12.5 grams sodium bisulfite (25% excess) in 50ml. of water added 9.9 grams (0.1 "m'olc)" of nj-butyl-isocyanatei The mixtureis s'tirred' rapidly for two hours atroom temperature. To the'clai solution,

are added 10 ml. of saturated sodium bisulfite soluti Crystallization of the s alt is complete after storagefovif night at 10'] C. 'll're precipitate isfilteredpwashed acetone and dried in a vacuum desiccator ovlerlphosphorusi It is then re i Example .I

Seventy ribbons of catgut,'six feet each in length (sixteen grams of collagen, based on dry weight) are immersed in a'200 ml. volume ofleach of 0.1%, 1% and. 5% aqueous solutions of tolylene diisocyanate sodium bisulfite adduct for a period of three hours at room temperature (2025 C.). Similar lengths of catgut ribbon are used as controls. The ribbons are removed, dried,,spun into. strings, wound on reels, sterilized, tubed,in,90%"isopropyl alcohol, and aged for two Weeks.

In a like manner seventy ribbons of catgut, six feet each in length (sixteen grams of collagen, basedon dry weight) are immersed in a 200 ml. volume ofieachof 0.1%, 1% and 5%; aqueous solutions of n-butyl-isocyanate bisufite adduct for a period of three hours at room t emperature(20+25 C.) using similar lengths as controls. After the tanning is complete, the ribbons aretreated as described above.

Samplesof eachof the ,tolylene-diisocyanate-treated catgut strings were tested for dry knot andwet knot tensile strengths on the' Scott incl-inedplane'testen. The results are shown below. Tensile strength is expressedasthe ratio between the average tensile strength in pounds and the diameterof the string in mils.- P.'D., hrsf? represents protein digestion time, as determined by the following.

procedure:

A 100 ml. volume of a buffer solution contain ing .l74 .22"

grams dibasic potassium phosphate and, 38:15. grams sodium bot-ate madenp to oneliter of water'ismixed with 76, grams thiourea, 800 ml. distilled .water and-I30 grams papain.. Just prior to testing; a. l-mlt-yolume of an= activatormade by dissolving 5.2 gramstsodium bisulfite; in.

water up to .a 100:m1;volume is added to24ml. of the buttered papain solution. The catgut string to lie-tested is.

immersed under twentygrams of tension in the: activated and buffered 'papain'solution, which is maintained'at an. incubation temperature of 37.8 C. r The period of time required for the catgut to be completely digested; ex

1 Tolylene diisocyanate sodium bisulfite adduct.

It will be seen from the results shown above that tolylenediisocyanate sodium bisulfite is an excellent tanning agent, the treated catgut showinga marked increase in dryknot tensileistrength and .en zyrnatic digestion time.

over the untreated control.

Example 5 II The eflect of; tolylene diisocyanate sodiumbisulfiteon catgut under varying conditionsofi concentration andtime, was determined. The ratioof catgut to volumeofsolution was the same as that used inExam pleI.

TABLE II TnlfBs Gonc'nlnTannlng Tannage Lbs. Tensile 11:13

Bath, Percent Time, Strength Hrs.

Hrs. Dry Knot 1 t 4 Example- III In another series of tests, the effect of tolylene diisocyanate sodium bisulfite on catgut under varying conditions of concentration and'time was determined. This series includes results on the wet knot,"as well as dry knot, strengths... Thev results are shown in Table III.

TABLE III Tannage Lbs. Tensile Strength TDI-BS Concn in Time; I. Tanning Bath, Percent Hrs. Hrs.

Dry Knot Wet Knot Example I V Seventy ribbons of catgut, six feet each inlength (six.- teen grams of collagen, based on'dry weight) are irn mersed in a 200 ml. volume of a 2% aqueous solution of.

hexamethylene diisocyanate. sodium bisulfite adduct, for a.

period o fthree hours at room temperature (20-25 C.).

Similar lengths of catgutribbons are used as controlsf. The ribbons. are removed, washed with water, spun into. strings, dried, .woundon reels, sterilized, tubed in isopropyl alcohol, and aged for two weeks.

In a likepmanner, seventy ribbons of catgut, sixv feet. each in length, aretreatedwith a 2% aqueous solution of. hexamethylene diisocyanate sodium bisulfite. adduct and the resulting ribbons are removed, spun. directly into strings without water washing, dried, wound on reels, sterilized,itubed in 90% isopropyl alcohol and aged for two weeks.

Both the washed and unwashed sutures were testedfor tensile strength properties in accordance with the pro The results are shown in Table" cedure described above.

TABLE IV Tensile Stren th HM-D-Bsf Oonc'n in Tanning, No. of T.S./d. g Bath, Percent Samples Dry Knot Wet Knot" 0 (control) 90 247 178' 2 washetL Q0 274 .214. 90 283 210 *Hexamethylene diisoeyanatesodium' bisulfite adduct.

What is'claimed is:-

1.. In amethod for preparing collagen sutures, the provement which comprises treating catgut with anaqueous solution of an alkalimetal bisulfite adduct of a compound selected from the group consisting oftolylene diisocyanate, hexamethylene diisocyanate and n-butylisocyanate at a temperature up to about 40 C.

2. A method as set forth in claim l'wherein the concentration of the alkali metal bisulfite adduct is from' about 0.25% to about 5%. a

3. In a method for preparing collagen sutures, the"irn=- provementwhich comprises treating catgut with an aqueous solution of an alkali metal bisulfite adduct of a compound selected from the group consisting of tolylenedi isocyanate, hexamethylene diisocyanate, and' n-butyl isocyanate at a temperature up to about 40 C., theratio ofcatgut tovolume of solution being 1:10 on a dry'weight basis;

4. A method as set forth in claim 3 wherein thevcomcentration of alkali metal bisulfite adduct is 'iromrabout 0.25% toabout 5%;

5. A method. as. set forthinclaim. 3nwhercinthe'treatment .is .carriedloutxat roonntemperature.

-aLa-L 6. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of tolylene diisocyanate sodium bisulfite at a temperature up to about 40 C.

7. A method as set forth in claim 6 wherein the concentration of tolylene diisocyanate sodium bisulfite is from about 0.25% to about 5%.

8. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of n-butyl-isocyanate sodium bisulfite at a temperature up to about 40 C.

9. A method as set forth in claim 8 wherein the concentration of n-butyl-isocyanate sodium bisulfite is from about 0.25% to about 5%.

10. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of hexamethylene diisocyanate sodium bisulfite at a temperature up to about 40 C.

11. A method as set forth in claim 10 wherein the con- 6 centration of hexamethylene diisocyanate sodium bisulfite is from about 0.25% to about 5%.

12. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of tolylene diisocyanate sodium bisulfite in a concentration of about 1%.

13. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of n-butyl-isocyanate sodium bisulfite in a concentration of about 1%.

14. In a method for preparing collagen sutures, the improvement which comprises treating catgut with an aqueous solution of hexamethylene diisocyanate sodium bisulfite in a concentration of about 2% Putnam Sept. 26, 1950 Evans et al June 14, 1955 

1. IN A METHOD FOR PREPARING COLLAGEN SUTURES, THE IMPROVEMENT WHICH COMPRISES TREATING CATGUT WITH AN AQUEOUS SOLUTION OF AN ALKALI METAL BISULFITE ADDUCT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF TOLYLENE DIISOCYANATE, HEXAMETHYLENE DIISOCYANATE AND N-BUTYLISOCYANATE AT A TEMPERATURE UP TO ABOUT 40*C. 